7.1 Standard is up to RC2. Yes, the installer is designed to give you a choice of grub or lilo. Or none, so you can skip the boot loader, then boot to Xubuntu and re-run its "update-grub". That should add VL to your existing boot menu.

Both should detect your current OS as long as you dont overwrite it. If you use advanced mode in the installer you can pick which bootloader to use (automatic uses grub2 by default.) or skip the bootloader installation entirely and as pointed out by Nightflyer, you can use your existing xubuntu to boot VL later.

And.. a word of caution regarding the "Automatic" mode: it will completely take over the hard drive, wiping out any existing installations. Use "Advanced" if you want to keep existing data on the drive.